1. Field of the Invention
The present invention relates to a recording/reproducing apparatus and a recording/reproducing system. More specifically, the present invention relates to a recording/reproducing apparatus and a recording/reproducing system, which use near-field light.
2. Description of the Related Art
In recent years, various technologies using near-field light as recording light have been proposed to realize higher recording density on an information recording medium (see, for example, Japanese Published Patent Application Nos. 2005-202987 and 2003-308632). The use of near-field light realizes a minute light spot beyond a diffraction limit of light can be realized. Therefore, for example, attentions have been paid on a heat-assisting magnetic recording technology using near-field light as a promising technology for high density magnetic recording. In addition, various applications of near-field light to an information recording medium using a magneto-optical recording film and a phase-change recording film have been proposed.
A recording/reproducing apparatus proposed in Japanese Published Patent Application No. 2005-202987 performs information recording on recording layers (recording mark regions) each having a fine structure not larger than the wavelength of incident light by irradiation of near-field light from a minute opening of a probe where the diameter of the opening is not larger than the wavelength of the incident light. In Japanese Published Patent Application No. 2005-202987, furthermore, an optical information recording medium includes recording layers (recording mark regions) with circular fine structures formed independently from one another when viewed from the light-irradiation side.
A recording/reproducing apparatus proposed in Japanese Published Patent Application No. 2003-308632 performs information recording on recording layers formed on fine structure layers not larger than the wavelength of incident light by irradiation of near-field light from a minute opening of a probe where the diameter of the opening is not larger than the wavelength of the incident light.
As a method of generating near-field light other than one using a probe as described in the above patent documents, for example, there is a method using surface plasmon resonance generated on the surface of a conductor when light is irradiated on the conductor. In this method, for example, if the polarization direction of light is aligned with the longitudinal direction of a rectangular conductor formed on a transparent substrate when light is irradiated on the conductor, electric charges are localized in the conductor under the electric field of incident light.
Oscillation generated by localization of the charges is known as surface plasmons. When a resonance wavelength of surface plasmons is equal to a wavelength of incident light, surface plasmons are brought into a resonance state called surface plasmon resonance. In this case, the conductor becomes an electric dipole, which is strongly polarized in the longitudinal direction of the conductor. When the conductor becomes the electric dipole, a large electromagnetic field is generated near the both ends in the longitudinal direction of the conductor to generate near-field light.